Normal07.8 磅02falsefalsefalseEN-USZH-CNX-NONEMicrosoftInternetExplorer4Effects of Heating Inside and Outside the Compound Sonic Point of the Solar Wind

美国Alabama大学Gary Webb博士

Normal07.8 磅02falsefalsefalseEN-USZH-CNX-NONEMicrosoftInternetExplorer4时间：2014年5月21日（周三）上午10:00-11:50

地点：空间科学楼南211

Normal07.8 磅02falsefalsefalseEN-USZH-CNX-NONEMicrosoftInternetExplorer4Normal07.8 磅02falsefalsefalseEN-USZH-CNX-NONEMicrosoftInternetExplorer4内容简介:We revisit the problem of the effect of heat addition in the solar wind including Alfven wave pressure as well as the plasma pressure (proton plus electron pressure). It is well known that the mass flux per unit area in 1D gas flow maximizes when the flow speed equals the sound speed and this result also holds in the presence of Alfven waves in which the wave energy exchange equation yields the wave action flux conservation law when their contribution to the compound sound speed is taken into account. The analysis proceeds along the line of calculating the changes induced in a steady flow along a tube (Laval nozzle) by the addition of amounts of heat and momentum, using a thin slice approximation which leads to Rankine Hugoniot type relations for weak deflagrations or detonations. The effective polytropic index gamma and flow speed relative to the compound flow speed ahead of the slice play crucial roles in determining whether local acceleration or deceleration results. Some results are at first sight unexpected since gamma for Alfven waves ranges from -1/2 in sub-Alfvenic flow to 3/2 in super-Alfvenic flow.

报告人简介：Dr. Gary Webb is a Research Scientist with the University of Alabama in Huntsville. He received his PhD degree from University of Tasmania, Austrilia in 1976. He has published more than 130 refereed publications. He has broad interests in the field of space plasma physics. On plasma physics, he has extensive experience working on Magnetohydrodynamics and gas dynamics theory：Variational Principles, Hamilton's principle；Noether's Theorems and Conservation Laws；Lie Symmetries, Fluid Relabeling Symmetries；Magnetic helicity, cross helicity and fluid helicity with application to space plasmas (e.g. nonlinear Alfven waves, magnetic flux ropes etc). On cosmic rays, he has worked on Cosmic Ray Transport and Acceleration in the heliosphere and in the galaxy (e.g. shear acceleration by Jets, pitch angle transport or focused transport equations for cosmic rays).Normal07.8 磅02falsefalsefalseEN-USZH-CNX-NONEMicrosoftInternetExplorer4